April 08, 2014
1 min read

Intraoperative AS-OCT measurement of lens capsule allows for accurate IOL power calculation

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TOKYO — A microscope-mounted anterior segment optical coherence tomography prototype allows for accurate measurement of distances within the lens capsule during cataract surgery, leading to precise IOL power calculation.

“Exact IOL power calculation is crucial with today’s premium IOLs. We have advanced technologies now, like optical biometry, and lots of mathematical formulas, but prediction is still not as accurate as it should be,” Oliver Findl, MD, said at the World Ophthalmology Congress.

The EUREQUO database of nearly 1 million cataract surgeries shows that 22% of eyes have more than 1 D of prediction error.

“With intraoperative AS-OCT, I do a scan of the eye during surgery, on the empty bag after lens removal. I use no viscoelastic but keep the infusion with a low bottle height to maintain a steady 20 mm Hg pressure and measure the distance to the anterior capsule and to the posterior capsule. In this way, I have an accurate prediction of where the lens should be,” Findl said.

In a trial including 70 eyes of 70 cataract patients — 30 emmetropic, 10 myopic and 30 hyperopic — this method was accurate in predicting IOL power.

“We had very good refractive outcomes, better than using classic formulas. There is still some variability, but at least we are one step further and we hope this method will make a difference, particularly for short eyes,” Findl said.

Variability was likely due to unpredictable amounts of fluid going through the zonule during surgery and hydrating the vitreous.

“The hydrated vitreous pushes the capsule forward and modifies the capsule size,” Findl said. “We are doing further studies, and by the end of the year, we will have results on 270 eyes.”

Disclosure: Findl is a consultant to Zeiss, which produced the prototype. He is a patent holder of the concept of measuring intraoperative capsule position.